Dry lamination is a process in which two or more kinds of films are bonded together by using dry laminating equipment and adhesives. The amount of adhesive used in dry lamination is very small, but it has a very important influence on the quality and performance of the composite film. It determines the peel strength of the composite film, and affects the transparency, heat sealing strength, heat resistance, dielectric resistance, etc. Therefore, the selection and use of adhesive for the composite film manufacturers are very cautious. Generally, two aspects are mainly considered: one is the selection of adhesive varieties, different types of adhesives are selected for products with different requirements; the other is that different coating amount (adhesive amount on dry basis) is also specified for products with different requirements. The quality control of dry composite membrane is basically guaranteed. According to my investigation, at present, domestic composite enterprises often ignore another important indicator - adhesive coating state, which has a greater impact on peel strength, transparency, heat sealing strength, etc. Many apparent defects are often caused by poor coating state, such as bubbles, spots and other defects, one of the main reasons is poor coating state. The coating state of adhesive refers to the distribution state of adhesive on the film. The standard state should be the distribution of adhesive on the film. The standard state should be that the adhesive forms a uniform, transparent and defect free adhesive film on the surface of the film. However, due to the complexity of the actual production, many factors in the production process will affect the coating state of the adhesive. It is very difficult to achieve the ideal standard state. Our work is to take appropriate measures to reduce the defects of this adhesive film to the minimum, until it does not affect It affects the quality of the composite film. Here, I would like to start from the equipment coating control system, raw materials, workshop environment and technology and other factors to discuss with friends the factors affecting the adhesive coating state and the corresponding solutions. 1、 The coating control system of equipment itself has the following four parts: 1. Cot - wire roller - scraper - glue tank system. This system determines the coating amount of adhesive and ensures that the adhesive is spread on the surface of film with a certain distribution density. The coating state of adhesive is mainly determined by this system. 2. Flattening roller flattening roller can further uniform the coating of adhesive and eliminate some traces of wire mesh. 3. The temperature and ventilation of oven system affect the evaporation rate of solvent and the hardening rate of adhesive. 4. Compound roller rubber roller this system provides a certain temperature and pressure, not only to further activate the adhesive, but also to further spread the adhesive, and further eliminate the fine defects of the adhesive. 2、 In general, the leveling property of general adhesive is better than that of cooking adhesive, and the leveling property of adhesives produced by different manufacturers is also quite different. In order to ensure excellent coating state, composite manufacturers should carefully identify and use. 2. If the surface tension of the adhesive film or the bottom film is too low and the difference between the surface tension and the adhesive surface tension is too small, the adhesive can not be fully dispersed and compatible on its surface. General film surface tension and adhesive surface tension difference is greater than 12 dyne, lower than this value, coating state may have problems. In addition, we should pay attention to the precipitation of additives in the adhesive film or bottom film. At present, the composite manufacturers have a deep understanding of the precipitation of additives caused by the long storage time of PE films with thickness greater than 60 μ, but the understanding of the auxiliary precipitation of pet and NY is not enough. It is generally believed that the surface tension of pet and NY is high, and there will be no problem in dry lamination. However, a large amount of additives are added to pet and NY during production. If the storage time is too long or the storage temperature is high, there will be the same A large amount of auxiliaries precipitate, which seriously affects the layer and affinity of the adhesive on the film surface. As the composite manufacturers are willing to use pet and NY as the carrier film, this must be paid attention to. Random corona treatment is a better solution. 3. Ethyl acetate ethyl acetate is a general binder diluent. The content of water or alcohol in ethyl ester has a great influence on the coating state of adhesive. The volatilization rate of water is much lower than that of ethyl ester. If the water content exceeds the standard, the evaporation rate of solvent will be seriously reduced, and the spreading rate and hardening rate of adhesive will be affected. Moreover, the adhesive itself can not be compatible with the film surface soaked by water. In addition, the curing agent and water or alcohol can produce CO2 rapidly, which not only limits the infiltration of adhesive, but also produces serious bubbles. 3、 Process factor 1, the working concentration of adhesive and the matching of wire roller, in order to improve the glue amount, it is generally solved by increasing the working concentration of adhesive (i.e. the content of working solid). However, it must be considered that only combined with the wire number of the wire roller, the good coating effect can be achieved. Only by adjusting the working concentration, the requirements can not be met. Generally, such a principle can be followed: the higher the working concentration, the greater the coating viscosity, the less the number of wires should be selected, that is, the mesh roller with large mesh volume. Generally 75% solid content, viscosity of 3000-5000 CPS, 25 ℃ adhesive (ordinary adhesive generally in this range), using 100-150 wire mesh roller,When the working concentration is in the range of 30%, it can meet the requirement of coating amount in the range of 2.0-3.5g/m2 (dry basis coating amount). However, the cooking concentration at high temperature is relatively large, and the viscosity is 3000-4000cps at 25 ℃ when the solid content is 50%. If the coating amount is 4.5-5.5g/m2 (dry base coating), it is difficult to ensure good coating condition by using wire roller with more than 100 lines. At this time, 80 wire mesh roller should be selected. It is suggested that the composite manufacturer should equip three sets of wire rollers to produce almost all dry composite products, i.e. one set of 80 lines for high-temperature cooking bag products or products requiring coating amount greater than 4.5 g / m2 (dry); one set of 100-120 lines for the production of water boiling and ordinary aluminum foil bags, and the coating amount of general medium or vacuum products is between 3.0-4.0 g / m2 (dry); one set of 130-150 lines is used for For the production of common products, the coating amount is allowed to be below 3.0g/m2. 2. The cots in the coating system provide a certain pressure to force the adhesive to extrude from the mesh and disperse on the surface of the film. The hardness of the cot has a great influence on the dispersion of the adhesive. There are two aspects to be noted. First of all, the hardness of domestic cots is not high, and the hardness of products from different manufacturers varies greatly; secondly, the hardness of COTS will decrease with the extension of service time. 3. The cleaning of the system, the cleaning of the wire roller is very important. The degree of mesh blockage affects the coating effect of the adhesive and the uniformity and continuity of the adhesive film, especially two aspects. First of all, we must adhere to regular cleaning, here refers to the use of mesh roller cleaning agent thorough cleaning, and to use the standard operation method; second, in the replacement of different varieties of adhesive, to carefully clean, to prevent the adhesive due to this pollution and affect the adhesion performance and coating effect. 4. When installing the circulating glue suction system, a large amount of air will be trapped in the preparation and mixing of the adhesive, which is not easy to disperse, especially when the high-temperature cooking adhesive is used. In the process of pouring the adhesive into the glue tank, a large amount of air will be entrained. The existence of air not only limits the spreading of adhesive, but also causes a large number of bubbles in the composite film. If the circulating air extraction system is installed, on the one hand, the dumping mode can not be used to reduce the air entrainment, on the other hand, the trapped air can be extracted to ensure the uniform coating of adhesive. 4、 Workshop environment 1, workshop humidity also seriously affect the coating state of adhesives, general humidity greater than 70% will not guarantee the normal coating state. Especially in summer, the workshop temperature is high, ethyl ester volatilizes in the coating system, resulting in the coating system temperature is quite low, water vapor in the cots and wire roller part of a large amount of condensation, damage the coating state of the glue, and will seriously reduce the performance of the adhesive. 2. The dust in the air of dust workshop will adhere to the adhesive film and cannot be removed, which will damage the uniformity and continuity of the adhesive film. Especially at the air outlet of the oven, the strong airflow will pick up dust particles and scatter on the adhesive film, seriously affecting the appearance. Therefore, in addition to keeping the workshop clean, the filter screen at the air supply outlet must be cleaned frequently.
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, the world's manufacturing city, is a subsidiary of Beite packaging (China) Co., Ltd., with a plant area of 6000 square meters. It is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of domestic advanced production equipment, a scientific and humanized management system and a group of experienced technical personnel For backing, to provide customers with quality products and first-class service.
The company produces composite bags, roll film, fruit bags, aluminum foil bags, suction mouth bags, self-supporting bags, zipper bags, anti-static bags, special-shaped bags, etc., which are suitable for the internal and external packaging of food, daily chemicals, electronics, toys, medicine, cosmetics, industrial products and other industries.
We uphold the integrity of cooperation, good quality, good service business philosophy, won the industry's approval, products sold to all over the world; welcome friends from all walks of life to inquire, visit our factory to investigate guidance and business negotiations.